Top 72 Database Design / Normalization Interview Questions & Answers (2026)

01 What is a database? 02 What is a DBMS? 03 What is a relational database? 04 What is a primary key? 05 What is a foreign key? 06 What is normalization in databases? 07 What is First Normal Form (1NF)? 08 What is Second Normal Form (2NF)? 09 What is Third Normal Form (3NF)? 10 What is Boyce-Codd Normal Form (BCNF)? 11 What is an index in a database? 12 What is the difference between a clustered and non-clustered index? 13 What is a composite index? 14 What is SQL and what are its main categories of statements? 15 What is a JOIN in SQL? 16 What are the differences between TRUNCATE, DELETE, and DROP? 17 What is a transaction in a database? 18 What does ACID stand for in databases? 19 What is referential integrity? 20 What is a schema in a database? 21 What is the difference between CHAR and VARCHAR? 22 What is an entity-relationship (ER) diagram? 23 What is a view in a database? 24 What is a stored procedure? 25 What is a trigger in a database? 26 What is the difference between UNION and UNION ALL? 27 What is an aggregate function in SQL? 28 What is GROUP BY in SQL? 29 What is a subquery? 30 What is the difference between WHERE and HAVING? 31 What is a NULL value in databases? 32 What is a surrogate key vs natural key? 33 What is data integrity? 34 What is the difference between a table and a view? 35 What is an auto-increment or serial column? 36 What is a unique constraint? 37 What is the difference between SQL and NoSQL databases? 38 What is a CHECK constraint?

01 What are database anomalies and how does normalization prevent them? 02 What is denormalization and when is it used? 03 What are isolation levels in database transactions? 04 What are dirty reads, non-repeatable reads, and phantom reads? 05 What is query optimization and what is a query execution plan? 06 What is a covering index? 07 What is database partitioning? 08 What is a materialized view? 09 What is the difference between OLTP and OLAP? 10 What is a star schema vs snowflake schema? 11 What is database replication? 12 What is connection pooling in databases? 13 What is a common table expression (CTE)? 14 What are window functions in SQL? 15 What is the difference between horizontal and vertical scaling of databases? 16 What is an ORM and what are its trade-offs? 17 What is the difference between optimistic and pessimistic locking? 18 What is database migration strategy for zero-downtime deployments? 19 What is a deadlock in databases and how is it resolved? 20 What are database constraints and what types exist? 21 What is index selectivity and why does it matter? 22 What is a self-join and when is it used? 23 What is schema migration versioning and why is it important?

01 What is database sharding and what are its challenges? 02 What is the CAP theorem? 03 What is eventual consistency? 04 What are MVCC and write-ahead logging (WAL)? 05 What is the difference between 4NF and 5NF? 06 What is a database cursor and when should you use one? 07 What is full-text search and how does it differ from LIKE queries? 08 What is database CDC (Change Data Capture)? 09 What is the difference between a heap table and an index-organized table? 10 What are common anti-patterns in database design? 11 What is a time-series database and when do you use one?